1: Don't Make Me Think
Krug's first principle of usability is "don't make me think."
This means that, as far as possible, the online experience should be elf-evident. The user should be able to understand how to use a site to do what he wants to do without having to figure out how it works.
In conversational terms, this means the user should not be asking, "what is this? What does it do? How do I do this?" but instead to be able to state "I know what this is, I know what it does, and I know how to do what I wish."
Things that Make Us Think
One thing that makes us think is when a web site doesn't speak in our language. A person looking for a job will find "jobs" very quickly. He likely learned that things such as "employment" or "career" mean that they lead eventually to job listings (among other things). If the designer gets clever and calls it "joborama" the user does not have a clear an immediate sense of what is behind that link.
Another thing that makes us think is elements that are interactive. There are fairly standard appearances for things like links (underlined text that is a different color from the rest) that the user has learned "do something" when they click on them, from their experience on other websites. When a designer does something clever, like removing the underlining or making it the same color as the rest of the site, the visual indicators have been removed, and the user must figure out which elements on the page can be clicked.
A third thing are tasks that require the user to go through an unusual sequence of steps. When booking a flight, the user has in mind where he is going and when he needs to go and expects to tell you that first. If instead you ask for the information about the return flight first, the user's train of thought is disrupted and he feels a sense of anxiety - he may eventually get through it, but he must pause to think about your process rather than following the one he expected.
(EN: Krug does not consider the question, "How do we know what the user knows?" The problem with many designers is they assume the user knows nothing at all and designs for the novice - which can be frustrating for the average person if he happens to not be an idiot. The travel app is a great example, in that the designer assumes the user doesn't know airport codes. But anyone who travels regularly knows the codes - and wishes to go from DFW to JFK - is rather vexed when they have to enter "Dallas TX" than choose an airport and then "New York NY" and then have to choose an airport. Granted, assuming all site users are experienced travellers might also be a mistake. The answer is market research, to find out what people actually do know rather than assuming.)
Self-Evident vs. Self-Explanatory
There's a distinction to be made between these two concepts: self-evident means that something can be understood at a glance, whereas self-explanatory means that something can be understood with a moment's pause to consider the information provided.
To return to the previous example: a button that says "jobs" is self-evident because it presumably matches what the user is looking for. The button that says "joborama" is not self-evident, but if there's a line of text beneath it that explains "find out about job openings" then the page has explained what the button does, and it's self-explanatory.
Naturally, self-evident is faster and better than self-explanatory because there is no pause during which the user must read and interpret, but not all things can be self-evident. When the user has no experience of a task, there is no knowledge that can be drawn upon.
Your Competition is One Click Away
Here, Krug mentions the scariest aspect of the Internet (for vendors): leaving your site and going to a competitor is very simple. They don't have to walk or drive to do it, they just have to click away. People, like water, follow the path of least resistance - and they will eventually decide that your process is to difficult and leave to try their luck somewhere else.
(EN: This is known in principle, and seems to be good, but curiously no-one seems to have done much to test the capacity for effort. Where, exactly, is the tipping point where the user will give up and start over rather than trying to continue? That's subject to speculation, and the basis of many arguments in which people have opinions and no-one has facts.)
He does mention there are exceptions to this:
- If you have a monopoly and there is no competition, they feel they must do business with you or do without
- If there is sufficient value to be gained (e.g. you are offering a very cheap price and leaving means paying more)
- If they feel that starting over will be more onerous than soldiering through
- If they feel that the competition will be just as difficult (or more) to deal with
He also concedes a psychological proclivity of man to refuse to quit when he really should. Some people invest their ego in completing a task and fail to consider the return on effort. Others consider the sunk cost of effort (I've waited half an hour for the buss, and that time will be wasted if I give up now). None of this is rational, but then, people are not rational.
For the most part, people expect things to be easy to do - and their enthusiasm and motivation to see their intentions through in action is based on this assumption. Any difficulty they encounter decreases that enthusiasm, to the point where they will give up.
The job of the designer, and the job of the merchant in general, is in feeding rather than undermining enthusiasm - which can best be done by making things self-evident and effortless.